Unless otherwise indicated herein, the description provided in this section is not itself prior art to the claims and is not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations each radiating to define a respective coverage area in which user equipment devices (UEs) such as cell phones, tablet computers, tracking devices, embedded wireless modules, and other wirelessly equipped communication devices (whether or not operated by a human user), can operate. In turn, each base station may be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. With this arrangement, a UE within coverage of the network may engage in air interface communication with a base station and may thereby communicate via the base station with various remote network entities or with other UEs served by the base station.
Further, a cellular wireless network may operate in accordance with a particular air interface protocol or “radio access technology,” with communications from the base stations to mobile terminals defining a downlink or forward link and communications from the UEs to the base stations defining an uplink or reverse link. Examples of existing air interface protocols include, without limitation, Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Wireless Interoperability for Microwave Access (WiMAX), and Global System for Mobile Communications (GSM), among others. Each protocol may define its own procedures for registration of mobile terminals, initiation of communications, handover between coverage areas, and other functions related to air interface communication.
In accordance with the air interface protocol, each of the one or more coverage areas of such a system may operate on one or more carrier frequencies and may define a number of air interface channels or specific resources for carrying signals and information between the base station and UEs. By way of example, each coverage area may define a pilot channel, reference channel or other resource on which the base station may broadcast a pilot signal, reference signal, or the like that UEs may detect as an indication of coverage and may measure to evaluate coverage strength. Further, each coverage area may define a downlink control channel for carrying system information, page messages, and other control signaling from the base station to UEs, and an uplink control channel for carrying service requests and other control signaling from UEs to the base station, and each coverage area may define downlink and uplink traffic channels or the like for carrying bearer traffic between the base station and UEs.
When a UE initially enters into coverage of a wireless communication system (e.g., powers on in coverage of the system), the UE may detect a reference signal and read system information broadcast from a base station and may engage in a process to register itself to be served by the base station and generally by the system. For instance, the UE may transmit an attach message on an uplink control channel to the base station, and the base station and/or supporting infrastructure may then responsively authenticate and authorize the UE for service, establish a record indicating where in the system the UE is operating, establish local profile or context records for the UE, and provide an attach accept message to the UE. Thereafter, the UE may then be served by the system in an idle mode or a connected/active mode. In the idle mode, the UE may monitor a downlink control channel to detect page messages and other information regarding incoming communications and may similarly transmit uplink control signaling to initiate communications or for other reasons. In the connected/active mode, the UE may have particular traffic channel resources assigned by the RAN, which the UE may use to engage in communication of bearer traffic and the like.
When a UE is served by a base station, the UE may regularly monitor the reference signal from that base station and reference signals from other base stations in the vicinity, to help ensure that the UE continues to operate in a most appropriate coverage area. If the UE finds that one or more other base stations provide sufficiently strong coverage, perhaps sufficiently stronger than the UE's current serving base station (source base station), then the UE may engage in a handover process by which the UE transitions to be served by another particular base station (target base station). In the idle mode, the UE may do this autonomously and might re-register with another base station. Whereas, in the connected/active mode, the UE may transmit to its serving base station a measurement report that specifies the one or more detected coverage areas and, for each such coverage area, the detected signal strength. The serving base station and/or associated network infrastructure may then decide based on the UE's measurement report to process a handover of the UE to a particular target base station from which the UE detected sufficiently strong signal strength.
Generally, a wireless service provider may implement many “macro” base stations throughout its RAN, to provide UEs served by those base stations with widespread cellular coverage. Such macro base stations may include a tall antenna tower and may operate at a high transmission power for providing a larger range of coverage. In recent years, however, the cellular wireless industry has begun to expand beyond traditional macro base stations, by now deploying small cell base stations, or “small cells,” such as a femtocells, picocells, or microcells, or other small scale base stations, typically having a much smaller form factor and operating at lower transmission power for providing a smaller range of coverage. A typical small cell may be about the size of a WiFi access point and may connect with a broadband wired/wireless connection to the Internet and establish a virtual private network (VPN) connection via the Internet with the wireless service provider's core network. The small cell may radiate to define a wireless coverage area in much the same way that a macro base station does. The small cell uses the broadband Internet connection to connect with the wireless service provider's network and to provide much of the same functionality as a macro base station. A small cell may provide service on a single carrier frequency (or on a single carrier frequency per technology, where multiple technologies are supported), and also transmit administrative messages and parameters that UEs can use to connect with the small cell.
Small cells serve the beneficial purpose of allowing subscribers to improve cellular coverage, perhaps in locations where the macro base station does not provide adequate coverage. As such, a wireless service provider may position small cells in areas that need added coverage, such as on lamp posts, utility poles, and the walls of tall buildings. Further, individuals and companies may acquire small cells from a wireless service provider and may position the small cells at desired locations, such as within a house or throughout a corporate campus.